Weird problem with tool compensation on large radius

[kerrigan007]

Hi all!
I'm new to the site and I'm hopeful some of you can have some leads on my current problem. I apologize in advance if I'm not clear enough, since English is not my first langage.
I'm machining a part that is about 42 inches long, 1.218 wide. Both sides are radiuses, slightly different (167.786 inch and 169.014 inch). We rough the part with a 2-inch cutter, then finish it off with a 1/2 endmill. I can put a negative tool compensation on the cutter without any problem. As soon as I try it on the endmill, it cuts the radius wrong, even if it's only -0.0001 as a compensation. I end up with measurings like 1.210 at both ends, and good measuring at the center only. Without any compensation, everything is fine so we know the program is correct. We tried many things so far. We got the backlash fixed last week with a company that aligned everything with a laser. Parameters for the backlash are ok. We think it's another parameter, but we don't know which one. This problem occurs only with 1/2 endmill and nothing else.

The machine is a Mazak V655-60 with Mazatrol M plus control (made in 1996).

Any ideas? Next step is to hire a Mazak guy...

Thanks.

 

[mhajicek]

What do the lead-in and lead-out of your program look like?

 

[kerrigan007]

What do the lead-in and lead-out of your program look like?

We machine all around, I have at least the radius of the tool as a lead-in plus a couple hundreds. As soon as I try to add a negative compensation, it affects a lot in Y- but does nothing special in Y+ (at least it removes what it is supposed to but not more). I just don't understand why removing practically metal dust (0.0001) has such a huge impact but only at the front of the part and at the ends. Because of this problem, we can't do much precise segments like this. I don't know if it's useful information but it's climb milling and the problem presents itself while going X-.

 

[mhajicek]

I'm pretty sure no one will be able to diagnose this without seeing your code. It would at least remove that variable, if there are no issues with it.

Is your lead in a perpendicular line? A tangent line? A line into an arc tangent to the part? Some older controls don't like some of those options.

 

[angelw]

I can put a negative tool compensation on the cutter without any problem.

When a negative Tool Radius Compensation is registered, it flips whatever the

Hi all!
I'm new to the site and I'm hopeful some of you can have some leads on my current problem. I apologize in advance if I'm not clear enough, since English is not my first langage.
I'm machining a part that is about 42 inches long, 1.218 wide. Both sides are radiuses, slightly different (167.786 inch and 169.014 inch). We rough the part with a 2-inch cutter, then finish it off with a 1/2 endmill. I can put a negative tool compensation on the cutter without any problem. As soon as I try it on the endmill, it cuts the radius wrong, even if it's only -0.0001 as a compensation. I end up with measurings like 1.210 at both ends, and good measuring at the center only. Without any compensation, everything is fine so we know the program is correct. We tried many things so far. We got the backlash fixed last week with a company that aligned everything with a laser. Parameters for the backlash are ok. We think it's another parameter, but we don't know which one. This problem occurs only with 1/2 endmill and nothing else.

The machine is a Mazak V655-60 with Mazatrol M plus control (made in 1996).

Any ideas? Next step is to hire a Mazak guy...

Thanks.

For a start, if the part is to be consistently 1.218" wide, one of your radii is wrong. 169.014 - 167.786 = 1.228, not 1.218".
If both radii share the same centre and a thickness of 1.218 is the target, this can be achieved by modifying the Tool Radius Comp value, but in doing so, the 42" length would be 0.010" undersize.

Is the program you're using a Mazatrol program of EIA?

Regards,

Bill